The present invention relates generally to a surgical retractor and more specifically to a surgical spinal retractor designed to facilitate certain delicate surgical procedures. The present invention relates more specifically to a retractor that will better aid in the exposure of the thoracic and the lumbar spine during certain hardware insertion procedures.
It is now well recognized in the medical profession that back pain and pain in the extremities is often a direct result of pressure on the nerves of the spinal cord due to narrowing of the spinal column or misalignment of the vertebrae. The spine can be compressed by encroaching arthritic spurs, ruptured discs, enlarging soft tissue masses such as tumors, and pressure from infectious processes. In years past, these conditions of the spine were surgically corrected by bone decompression and soft tissue removal in association with a procedure called a fusion. Strips of grafted bone were placed adjacent to the vertebral segments causing them to grow together or "fuse". The resultant rigidity and realignment prevented further pressure on the nerves and stabilized the spinal column. In certain cases metal rods and hooks were attached to the bones to hold them in a specific position while they fused together.
In the past four to five years, these procedures have changed and there has been a dramatic increase in the use of spinal instrumentation devices in the treatment of this problem. Briefly, these devices involve the application of rather large screws, bolts, bars, and sometimes even rods in order to stabilize the spine. However, there has been an ongoing struggle to obtain adequate exposure of the bone structures surrounding the nerves making up the spinal column in order to insert the stabilizing devices. Because of the delicate nature of the surgery and the critical demand for visualization and placement of the stabilizing hardware, a need has developed for a retractor which allows better visual access to the spine and mechanical access to the bone structure where the hardware is being inserted.
In today's market, many different types of retractors are available which employ rack and pinion devices for the purpose of powering the retractor mechanism and holding the tissues apart. However, the retractor blades (the part of the distraction mechanism that actually enters into the wound and holds the muscle apart) currently available are a hinderance to visualizing the bones of the vertebral column and physical access to the bone by the necessary instrumentation. This deficiency in the prior art is what has led to the development of the retractor blades of the present invention.
Up to this point, the retractors that have been available for use in spinal surgery employ two arms which are perpendicular to a rack and pinion apparatus which is used to crank the arms apart. Extending at right angles from the arms down into the wound are various-sized retractor blades usually with one or more small teeth on the bottom of them. This particular design is flawed in two respects. The first flaw in these prior art devices is due to their inability to handle the tension inherent in the muscles and the fascial tissues in the back when the retractor is cranked open to spread the wound. As the two arms of the retractor are spread, a situation is created much like a bow string being drawn against the bow frame; the further the string is drawn (or the retractor arms are spread), the greater the pressure against the frame. And in the case of the surgical retractor, additional pressure is created because the retractor blades are extending into the wound. The further the blades extend into the wound, the greater the pressure. Because the blades are connected to the arms at one end and their other ends extend into the wound, there is a levering effect from the pressure of the muscles and fascial tissue on the teeth ends of the blades causing the blades to rotate about the pivot point created where they are connected to the arms of the retractor. The overall effect of these mechanics is that most retractors tend to work their way upward out of the wound because of the compressive forces of the muscles and fascial tissues.
The second problem with the prior art devices is that because the arms of the retractor lie along the skin at the top of the wound, they lie immediately in the way of the application of pedicle screw instrumentation apparatus. In the current procedure, screws are placed into the lateral or side portions of the spine into small, angled, structural parts of the vertebral body of the spinal column. It is absolutely critical that these screws be put in at a certain angle at each level. If the retractor has not been distracted far enough on either side of the wound, the large arms of the retractor block the appropriate angle being applied for the reaming and the application of these pedicle screws. The result of this can be disastrous in that the screw can be misapplied, and tilting either too far inward or outward can result in nerve damage or ineffective stabilization of the spine.
One obvious solution to the second flaw with the prior art devices is to simply crank the retractor open farther to spread the wound wider. However, spreading the wound wider tends to create tears in the muscles and flesh and impede the healing process as well as creating more pressure on the blades of the retractor, thus causing them to be more prone to work their way upwardly and out of the wound.
It will thus be appreciated by those skilled in the art that there is a need to provide a retractor which can accommodate the requirements of this new procedure without having to spread the wound wider. The desired device would spread the wound to make the spine visually and mechanically accessible without creating excessive tearing of the muscles and fascial tissue and without creating excessive pressure on the blades of the retractor to cause them to work their way up and out of the wound. This device is presently lacking in the prior art.